Magnetic field effects on synthesis process of high-Tc superconductors

Materials synthesis processes in high magnetic fields are investigated for high-Tc superconductors at the High Field Laboratory for Superconducting Materials, Institute for Materials Research, Tohoku University. On a melt growth process of YBa2Cu3O7 bulk in magnetic fields, it was found that the crystallinity is improved. These results are due to not only the magnetic field orientation but also the decrease of the crystal growth rate by the magnetic field, which is suggested from a differential temperature analysis measurement in magnetic fields. On a chemical vapor deposition process of YBa2Cu3O7 films deposited on the polycrystalline Ag substrates in high magnetic fields, the microstructure changes drastically from the rectangular large grains with 10 μm in size to the small complex shaped grains. The spiral growth mode is observed for the samples prepared at 0 T but it changes into the island growth mode for that prepared in the presence of a magnetic filed. On a partial-melt process of Bi2Sr2CaCu2O8 tapes in magnetic fields, the homogeneous texture is obtained and it results in the increase of the critical current density.